Field of the Disclosure
The present disclosure relates to a workpiece fixing jig for fixing a workpiece on a table of a machine tool, and a workpiece fixing method for fixing a workpiece on a table of a machine tool using the workpiece fixing jig.
Background of the Disclosure
For example, a clamp unit as disclosed in Japanese Unexamined Utility Model Application Publication No. H4-9241 has hitherto been known as a workpiece fixing jig for fixing a workpiece on a table of a machine tool.
This clamp unit is composed of a positioning block having a shape formed by bonding a columnar part and a rectangular parallelepiped part, a hook clamp inserted in a guide hole bored in the columnar part along a center axis of the columnar part, a clamp bolt inserted through the hook clamp along the guide hole and screwed in a screw hole formed in the positioning block, and a tubular spacer having an arcuate cross section and detachably fitted on the columnar part. Note that, on this clamp unit, the upper surface of the spacer is a first reference surface and the circumferential surface of the columnar part is a second reference surface.
According to the clamp unit having the above-described configuration, a workpiece is fixed on a surface plate (table) with a plurality of the clamp units arranged as appropriate on the surface plate. That is, first, the positioning blocks of the plurality of clamp units are arranged as appropriate on the surface plate. Thereafter, the positioning blocks are fixed on the surface plate with a workpiece placed on the upper surfaces of the spacers (first reference surfaces) and in contact with the circumferential surfaces of the columnar parts (second reference surfaces). Subsequently, each hook clamp is turned around its axis until a portion of the hook clamp is positioned above the workpiece, after which the clamp bolts are tightened one after another. Thereby, the workpiece is pressed against the upper surfaces of the spacers by the hook clamps and clamped between the hook clamps and the spacers; consequently, the workpiece is fixed on the surface plate.